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For animal/non-human applications

Antibiotics are used also for other purposes than to treat bacterial infections in humans. As in human medicine, some of this use is prudent, while some is improper. Any antibiotic use runs the risk of promoting survival of resistant bacteria.

Examples of areas were antibiotics are used in the non-human sector:

In veterinary medicine to prevent and treat diseases in animals.

In food animal production. Large quantities of antibiotics are for instance used in high-intensity animal farms as mass-prophylaxis to large flocks of animals to decrease spread of disease or for treating disease epidemics. In some countries, antibiotics are also added to animal feed to increase growth of the animals (growth promotion).

When growing fruits and vegetables. Antibiotics are sometimes sprayed on or injected into fruit and vegetable crops.

In aquaculture, that is, when farming aquatic organisms such as fish and molluscs.

Food-animal production

Currently, large quantities of antibiotics are used for disease prevention and control and to promote growth in food-producing animals, often as a substitute for hygienic husbandry practices. Global antibiotic consumption in livestock was estimated at 131,109 tons in 2013. When antibiotics are used in an industrial setting, where large numbers of animals are kept in close proximity under often unhygienic conditions, a perfect setting for selection and spread of resistant bacteria is created.

What are the consequences for human health?

Scientists across the globe have provided evidence that antibiotic use in the non-human sector is a contributing factor in the development and spread of antibiotic resistant bacteria in the environment, as well as for some of the resistance and multidrug-resistance we see in human pathogenic bacteria. Read more in How did we end up here? – Antibiotics in the environment.

Consequences for human health – The example of colistin resistance

Colistin was used in human medicine between the 1950s and 1970s, after which its use diminished as safer drugs were developed. It was however not completely abandoned, and with increasing rates of multidrug-resistance, colistin was revived and recognized as a critically important antibiotic to be used as a last resort when all other therapies failed.

Meanwhile, colistin was marketed to farmers as an efficient food additive. Unfortunately, colistin use in agriculture lead to selection of resistance. When the mcr-1 gene was discovered, the disaster became apparent. mcr-1 provides colistin resistance and is located on a plasmid, a mobile genetic element. This makes it transferrable between different strains and even species of bacteria. Now, bacteria with mcr-1 has been found worldwide in the environment, animals and humans – even causing disease in patients.

The higher abundance of the mcr-1 gene in isolates from food animals compared to human isolates, the much higher use of colistin in animal farming compared to human medicine, and the finding of mcr-1 together with genetic elements typically seen in animal environments, indicates a flow from animals to humans.

Below is a selection of resources introducing the magnitude and scope of the problem.